1. Field of the Invention
This invention relates to a wireless communication system for performing communication by a wireless method, and more particularly, to a wireless communication system for performing wireless communication with a fixed station connected to a communication network or directly with an exchange.
2. Description of the Prior Art
Heretofore, in telephone communication for performing, for example, voice communication, there have been known various kinds of methods in which wireless communication is performed. They are, for example, a portable radiophone method (transmitting output: a few watts (W)) for performing wireless communication with a direct exchange (base station), such as a car telephone or the like, and a so-called cordless telephone method for performing communication with a network connecting device (base unit) connected to a wired communication network while moving only over a very restricted range such as indoors, using weak radio waves (transmitting output: a few milliwatts (mW)).
Although different communication protocols are used in these wireless telephone methods, the hardware configurations of these mobile terminals are similar. Nevertheless, a conventional device is configured exclusively for either the portable radiophone method or the cordless telephone method.
Consequently, in the case of a portable radiophone, use in a shielded structure is impossible, and in the case of a cordless telephone, conversation cannot be performed if there is not a base unit nearby. Therefore, in order to communicate while moving indoors and outdoors, heretofore, both portable radiophone and cordless telephone must be held. This results in a big investment in communication equipment.
Problems also arise because, although it may not be deemed difficult to unify both functions of the portable radiophone and cordless telephone, troublesome operations, such as switching of switches or the like, are required for selecting either of the functions, and communication cannot be performed if a switch setting is wrong. Moreover, although it is desirable to select cordless telephone communication where there is a base unit nearby and the cordless telephone method can be used, because communication cost is high for the portable radiophone which can be freely moved outdoors, there is a possibility that the expensive portable radiophone method may be selected due to an unoptionized switch setting in a zone where both communication methods are possible.